Yahoo Mail is a web-based email app that can be accessed on desktops and mobile devices. It offers one-tap access to the inbox, instant email alerts, and support for multiple Yahoo accounts. Users can customize the app with contrast themes, text resizing, and screen reader support. It also includes features such as document and image storage, travel confirmations, and package delivery tracking. Additionally, users can add Gmail, Outlook, and AOL email accounts for easier access.